Blue light is part of the visible light spectrum and is emitted by the sun and artificial light sources such as LEDs, computers, and smart phones. Some types of blue light can be beneficial and help regulate our bodies' internal biological clocks. However, blue-violet light can have a harmful impact on the eyes, specifically the retina. It is also a risk factor for the onset of age-related macular degeneration, a deterioration of the part of the retina responsible for sharp, central vision.Since some forms of blue light are necessary, Crizal Prevencia No-Glare lenses selectively block only the harmful types of blue light. New technology called Light Scan allows beneficial blue light to pass through the lens while filtering out the dangerous blue-violet light that can cause age-related macular degeneration.